"I don't like heights," he wrote. "1 don't like being on the water. I am upset by walking across parking lots or open parks or fields where there are no buildings . . . but do equally badly when I am closed in, as I am severely claustrophobic."Shawn's guilt at being "spared" and sense of loss at his twin's absence reverberate throughout the book, even as passages reveal his fear that "it was only a matter of time before the magic glue that held my own brain together would lose its adhesive properties, and I would join the lines of shuffling institutional dependents at Briarcliff," where [Mary, Shawn] lives.As for whether the process of reflecting on his parents and siblings and his relationships with them while writing Twin lent him a sense of "closure," Shawn says the opposite is closer to the truth: "If there's a noun to describe an opening, rather than a closing, I'd use that - maybe 'opensure'?" he laughs.